The present invention relates generally to accumulator injectors employed in fuel injection systems and relates more particularly to a new and improved accumulator nozzle fuel injection system providing improved control of both the fuel injection rate and the volume of the injected charge.
U.S. Pat. No. 4,566,416 entitled "ACCUMULATOR NOZZLE FUEL INJECTION SYSTEM", which patent is assigned to the assignee of the present invention, discloses an accumulator injector for a fuel injection system for a diesel engine. The disclosed accumulator injector has a fuel accumulator chamber connected to a fuel source by a passage having a restricted orifice. The pressure of the fuel source is controlled by an electronic controller. An injection valve control chamber is connected to the fuel source via a second passage having a restricted orifice. A solenoid valve which is controlled by the electronic controller is selectively energized to momentarily release pressure in the control chamber for injecting a charge of fuel from the accumulator chamber. The quantity of fuel in the fuel charge and the rate of injection of the fuel charge is determined by the fuel source pressure and the pulse width of the solenoid operating pulse.
The present invention is a new and improved accumulator injector having a modular form which incorporates many of the features of the foregoing accumulator injector of U.S. Pat. No. 4,566,416 to provide a new and improved accumulator nozzle fuel injection system for controlling the rate of fuel injection throughout the full speed and load range of the associated internal combustion engine. The present invention is particularly adaptable for use in engine applications wherein the available space for nozzle installation is limited. In accordance with the present invention, an accumulator injector having a modular configuration is employed to provide an efficient means for controlling the quantity of fuel in the fuel charge. The modular configuration reduces production costs because the modular configuration makes possible the use of common components for many different applications and injector configurations. The modular configuration also makes possible the efficient removal of the solenoid unit from the accumulator injector so that in the event of an electrical problem in the solenoid unit, the solenoid unit can be replaced with a new preadjusted solenoid unit without dismounting the entire accumulator injector from the engine and without requiring adjustment of the mounted injector.
The accumulator injector also incorporates means for varying both the accumulator pressure and the time interval of the injection for establishing the rate of fuel injection and the quantity of fuel in the injection charge. Means are also provided for terminating the fuel injection event rapidly and abruptly to thereby avoid the undesirable end of injection fuel dribble or fuel throttling which reduces combustion efficiency and increases combustion pollutants.